The girl in the yellow dress twirling an umbrella in one hand and spilling a trail of salt with the other has become quite the polarizing icon.

Chefs, who consider common table salt pedestrian, snub her. Health advocates wag a collective finger in her face. But it’s the marketers who win this contest – they’ve figured a way to get upwards of $15 a pound for something the skipping gal peddles for two bits.

Yet geologists will tell you that salt is just salt: an ionic compound of gas and metal.

Salt is on everyone’s mind and everyone’s table. It’s the ingredient that has no substitute and no equal when it comes to dividing a crowd of foodies.

Long before humans decided to enliven their food with such a remarkable ingredient, positively charged sodium ions and negatively charged chloride ions were altering things around them in useful ways. The ionic compound was acting up, reacting with proteins and plant cell walls, especially when dissolved in water.

People have been collecting this indispensible ingredient since prehistoric times. But it’s only been in the last decade or two that foodies have jumped on the bandwagon, claiming to detect a world of difference between black, pink, fine, coarse and kosher, just to name a few.

“I’m not a big fan of iodized, fine-grain salt,” said Chris Crowl, chef proprietor of Cosmo Bar & Dining, explaining that the commercial processing is harsh and cleaning agents alter what should be in a natural, more pure form.

“The body doesn’t recognize highly refined table salt as easily,” Crowl said. “It doesn’t use it as it would other salts.”

A graduate of the Culinary Institute of America, Crowl prefers to use kosher salt for cooking and fine- and coarse-grain finishing salts for plated fresh vegetables.

But biochemist Christine Smith, who also is a certified nutrition and wellness consultant, disagrees with Crowl.

Smith, the owner and founder of You and Food Nutritional Research and Consulting, said the vast majority of any salt we eat – whether it is common iodized table salt or a fancy gourmet salt – is simply sodium chloride.

The FDA requires that U.S. food-grade salt be at least 97.5 percent pure sodium chloride. Common table salt is closer to 99 percent sodium chloride. And contrary to popular belief, fine-grain, white salt is not bleached with additives.

“We’re in an anti-white phase. We equate white with unhealthy,” Smith said, offering potatoes as an example of white food that gets an undeserved bad rap.

Smith said the color in gourmet salts often is from fine grains of volcanic clay, likely containing iron oxide, which makes these pricier salts actually less pure than common table salt.

Another common salt additive, iodine, a tasteless, odorless ingredient that can prevent goiter, is a necessary nutrient, Smith said. Iodine is plentiful in sea water fish, milk and some fruits and vegetables, depending on the soil in which they are grown. Iodine deficiency has been virtually eliminated in North America, where 70 percent of the salt sold is iodized, but goiter remains a problem in other parts of the world.

Certified nutritional consultant Becky Most-Reinfeld of Nature’s Oasis said all salt comes from the sea, but most is so highly refined that “it’s just a chemical. All the trace minerals, the building blocks of life have been stripped away,” she said.

Natural salts containing black volcanic minerals have an enhanced taste and a slightly acidic, intense feel on the tongue. Less salt is required to achieve a salty flavor, but many cannot discern the difference in taste.

“You have to wean yourself off the intense flavors of refined salts to appreciate the broader spectrum of more subtle flavors,” Most-Reinfeld said.

Not all salt experts would agree with Most-Reinfeld. Because the size of grains of salts differ, there can be some misleading sensory impressions that cause tasters to claim some salts as being saltier than others. A tablespoon of finely powdered salt will contain more salt by weight than a tablespoon of coarse-grain salt because it has less air space between the grains.

Most-Reinfeld said a bigger problem than excess salt consumption is the resulting lack of potassium and magnesium when diets come from processed foods, rather than being rich with fresh fruits and vegetables.

“Too much salt doesn’t cause high blood pressure. It’s too few nutrients in refined foods that upset the balance. Still, everybody should reduce their salt intake,” she said.

About 2,000 milligrams of salt a day is reasonable, but in a diet made up primarily of heavily refined foods, one large bowl of canned soup can contain half of that allowance, she said.

Salt not only tastes good, but it makes us feel good, too, said registered dietitian Marissa Kleinsmith of Paint Your Plate Nutrition.

“Ingestion of salty food creates a neurological food reward memory,” Kleinsmith said. “Like sugar, when we eat something salty, feel-good neurotransmitters are released in the brain, so our taste buds become trained to seek the taste to achieve that ‘feel-good’ state.”

Craving for salty foods can be dialed back, but it could take a few weeks to develop an appreciation for the subtle range of tastes in less-salted, nutrient-dense foods, Kleinsmith said.

A salt primer

Kosher salt

Kosher salt is produced by an alteration in the evaporation process that results in much larger and irregular-shaped grains that dissolve more slowly in liquid. Long-handled rakes are used to create the irregular surfaces that can do a better job of withdrawing blood from uncooked meat, important in the dietary laws of Judaism. The size of the grains of kosher salt varies considerably, making it difficult to convert measurements of fine-grain table salt to kosher salt. Used for brines and for seasoning when cooking, kosher salts are no purer or saltier in taste than refined salt.

Iodized salt

Iodized salt is formed when potassium iodide or a mineral salt containing potassium iodide is combined with sodium chloride. Kosher salt, sea salt and table salt all can be purchased in iodized or non-iodized forms. The practice of iodizing salt in the U.S. started in 1924 to lower the incidence of goiter. Iodine occurs in some dairy and seafood and in vegetables grown in coastal soils that contain salt from the ocean.

Fleur de sel

Literally “the flower of the salt,” fleur de sel is flake-like, delicate, crisp chips of salt. Fleur de sel is hand-harvested from the top layers of inland sea beds found in Brittany on the west coast of France and in coastal areas of Portugal. This light-gray, artisanal finishing salt, often used as a garnish, is labor-intensive to extract, which explains why fleur de sel is marginally cheaper than a ticket to France.

Sea salt

All salt is from the sea. Salt that is mined comes from evaporated ancient inland seas. Whether it came from the sea last week or was extracted from seas trapped under the ground millions of years ago, all salt is processed and purified for human consumption.

Pink salt, also Himalayan or Hawaiian salt

This mined salt contains 95 to 97 percent sodium chloride. The pink color may result from gypsum, iron oxide and up to 10 trace minerals. These salts are named for the areas from which they are mined, and crystals can range from fine to coarse.